Trunk circuit



Jan. 6. 192,5- 1,52"1,72s

W. B. STRICKLER ET AL TRUNK CI-RCUIT Filed Au z. '2, 1920 2 Sheets-Shet 1 Min In van for:

' Wa/ferB. Sfrick/en Y W. B. STRICKLER ET AL TRUNK CIRCUIT 7 Filed Au '7, 1920 2 Sheets-Sheet 2 lnven for:

Wa/fer B. 5frick/er' Paul L. Wrighf Patented Jan. 5, 3925.-

name ares WALTER B. s'rnrcxtnn. or EAST cannery, NEW JERSEY,- Ann PAUL 1.. WEIGHT, or

rarest omen.

new roan, n. rfassrenons To urnsrE-Rn ELEc'rarc ccrirAN lNGO'RPORATElIi,

pr nnw'Yoa x, 1v. GORroaAr on'oF YORK.

TRUNK CIRCUIT.

Application filed August 7, 1920. Serial No. 401,916.

' To all whom/it may concern: v

Be it known that we, WA R E. Simon LER and PA UL' L. VVRIGH T, citiZenso f the United States o't America, residing at East Orange, in the county 01 Essex, State of New Jersey, and New York, in the county of New York, State of New York, respectively, have invented certain new and.use-

ful Improvements in Trunk Circuits, of which the following is a full, clear, concise, and exact description.

This invention relates to trunk circuits for telephone systems, and particularly to trunk circuits of the repeating type. More particularly, the invention relates to a repeatingtrunk circuit tor use in extending calls from an outlying private branch exchange or subscribers station to an automatic telephone exchange .or from a toll switchboard orsubscriber in the automatic telephone exchange to the outlying private branch exchange or; subscribers station when. the distance between such private branch exchange or subscribers station and the toll switchboard or automatic exchange is greater than the average length of trunk circuits. In such instances, it is customary to furnish a trunk circuit of the repeating type in order to satisfactorily operate automatic switches at the automatic'exchange aswell as to increase the transmission range. A difliculty, however, arises in systems of this nature where it is desired to signal the outlying point over the repeating trunk circuit, the di'fficulty being, the unsatisfactory operation of the signalling device connected to the distant end of the trunk circuit due to the impulse repeating apparatus being connected to the trunk circuit.

It is, therefore, an object of this invention to provide in a system of this nature, an improved circuit for the transmission of impulses from the outlying point to the main exchange, to provide for the efiicient transmission of ringing-current for signalling purposes f OD the main exchange to the'outlying point and to provide means for increasing the range of common battery transmission. v

In accordance with the object of the invention, a trunk circuit, normally divided into inner and outersections but inductively united by means of a repeating coil, and ext d ng m op ietprs n sit en r s scribers station to an automatic exchange,

is provided with'improved' means for re-:

peat-ing impulses to said switches fortho station is provided.

" This and other features of the invention will more clearly appear in the following specification and the annexed drawings in which Fig. 1 shows diagrammatically an embodiment of the invention as applied to a trunk circuit for interconnecting a manual exchange and an automatic or toll exchange, and in which Fig. 2 shows'diagranimatically an embodiment of the invention as apcalls to the automatic exchange. Qn incomplied to a trunkcircuit for interconnecting a long line subscribers station with 'anautomatic exchange. By the term a long-line subscribers station is meant a station which is connected with a main exchange over a line which exceeds in length the average length of telephone lines.

In Fig. 1 of the drawings there is shown a portion of a cord circuit B, which. may be located at the operators position A, extends ing from jack 11 at the operators position to a distantexchange. over a trunk line T.

The trunk line ,T may terminate'atthe automatlc exchange in a non-numerical switch N and may be multipled to a jack 50 located at a toll operators position. Since the switches at the automatic exchange form no part of the present invention and may be of any well known type, they have been only diagrammatically represented. A called subscribe'rs stationG is shown as terminating in the contact bank of a connector switch C. The trunk circuit T is normally divided into inner and outer sections but inductively united by means of a repeating coil 15 As= sooiated with the inner sectionoi the trunk V circuit is a repeating relay 12'which is responsive to impulses from an impulse sender S of the cord circuit B and servestobridge the outer section of the trunk. Associated ith the inner section of the prank is a ring ns re pon v i -3 i 'i' iifi fi e il ien ing relay rom the trunk circuit. In the case of a recall, when plug 10 is inserted into jack 11, ringing responsive relay 12 of the cord circuit B is actuated causing the lighting of lamp as which serves as an indication to the operator that she is wanted. I

Referring to Fig. 2 of the drawing, there is shown a subscribers station M directly connected to a trunk circuit T The trunk circuit T terminates in, a non-numerical switch N at the automatic exchange. Accessible to the non-numericalswitch N is a connector switch K. A jack 150, which may be located at a toll oper-ators position E, is shown as multipled to the non-numerical switch N The cord circuit E is shown as having a ringing key 152 connected thereto. By'the actuation of the kley 152 ringing current may be proi ected over conductors 106 and 107 to signal the subscribers station M. The trunk line T is divided into inner and outer sections, said sections being normally united by means of a repeating coil 113. Associated with the inner section of the repeating coil 113 is an impulse relay 111. Under the COD"? trol of the impulse sender S atthe subscribers station M the impulse. relay 111 may be actuated to intermittently bridge the outer section of the trunk T to setthe connector switch K upon the terminal of the desired line. On incoming calls to station M, the ringing responsive relay 125 is energized which causes the energization of relay 127, which relay in operating conductively connects the outer section of the trunk cir cuit T to the inner section. Belay 127 in operating also disconnects the primary winding of repeating coil 113 and the impulse relay 111 from the trunk circuit.

It is thought that the nature of the invention may be more fully comprehended by the following description of the operation of the system shown in the drawings.

Referring first to Fig. 1 of the drawings and assuming that the operator at position B desires to extend a connection to the subscriber at station G whose line terminates at the automatic exchange in the connector switch 0, the operator will insert plug 10 of the cord circuit into jack 11, whereupon relays 13 and 12 will be energized over a path from ground, left hand winding of relay 12, winding of relay 13, upper left hand winding of repeating coil 15, upper normal contactsof relay 14, tips of ack 11 and plug 10, upper normal contact of key 17, winding of coil 18, lower normal contacts of key 17, rings of plug and jack 11, normal contacts of relay 11, lower left hand winding of repeating coil 15, lefthand normal contacts of slow-to-operate relay 16 and right hand winding of relay 12 to grounded battery. Relay 12 in operating closes a bridge including the upper right hand winding of repeating coil 15, retardation coil 23, lower right hand winding of repeating coil 15, and the front contact and armature of relay 12, across the conductors 21 and 22 of the outer section of the trunk. The closure of this bridge "causes the operation of the nonnumerical switch N at the automatic exchange in the well known manner and as soon as an idle s-witchsuch as C is selected impulse relay 20 of the switch G willbe operated over a ath extending, from ground, left hand winc ing of relay 20, terminal 4-5 brush 4.4, conductor 21, upper right hand Winding of repeating coil 15, winding of retardation coil 23, lower right hand winding of repeating coil 15, front contact and armature of relay l2, conductor 22 and brush 16, terminal 47, andright handwinding of relay 20 to grounded battery. For the purpose of simplicity a directively controlled switch C only has been shown but it will be understood that a number of selector switches may be interposed between the nonnumerical switch and the connector switch C. Relay 13 in energizing completes a circuit at its front contact and armature for slow-tooperate relay 16. Relay 16 in operating connects condenser 60 in series with the primary windings of the repeating coil 15 and opens its left hand normal contacts thereby connecting retard-coil 25 in series with relay 12. Relay 16 in operating at its right hand. alternate contacts connects ringing responsive relay 30 and condenser 28 across the outer section of the trunk. The insertion of the plug 10 into jack 11 discon nectsringing responsive relay 37 and lamp signal 39 from the trunk circuit.

The operator may then actuate dialing key 17 to connect the impulse sender or dial S with the cord circuit for the purpose of setting switch 0 upon the terminals of the desired line. Upon the first interruption of the circuit by impulse sender S relays 13 and 12 release their armatures. Relay 13 in releasing opens the circuit for slow-to-operate relay 16 which in retracting its armatures opens the circuitfor ringing responsive relay 30, short circuits retardation coils 23 and 25 and disconnects condenser 60 from serial relationship with the primary windings of repeating coil 15. Relay 12 in releasing its armature interrupts the bridge across the conductors 21 and 22. Relay 16 being slow-to-operate will not energize durmemes ing the remaining impulses of the series and retardation coils 23 and 25 and condenser 29 will remain short circuited and relay 30 and condenser 28 will remain disconnected during the sending ofthe remaining impulses of the series. Due to the disconnection of the condensers, the short circuiting otthe retardation coils and the opening of the circuit of relay 30 while impulses are being sent capacity and inductiveetlects upon the impulse relay 20' are prevented thereby providing an efiicient circuit; 7

After the necessary number of impulses has been sent to set brushes 70 and 71 of the connector switch C upon the terminals 72 and 73 of the desired subscribers line C, ringing current will be transinitted to the substation G in the well known manner. Upon the response of the subscriber at station talking current for the substation will be su qplied from relay 7 5. A-tter completion of conversation the operatorat position A. will remove the plug 10 of cord circui't B from jack 11, thereby restoring all relays of the trunk circuit T to normal and opening the bridge across the trunk condu'c tors 2'1 and 22, which causes the release of the switches at the automatic exchange in the Well known manner.

It willbe assumed that atoll operator desires to signal the operator at position A for the purpose of obtaining a connection with the subscriber whose line terminates thereat, Plug 51. of a cord circuit E (a portion only of which is shown) at the toll operators position will be inserted into jack ancl the key 52 actuated to project ring ing currentfrom a source 53, over the trunk, whereupon relay 30 of the trunk clrcut Wlll be energlzed over a path extending from I ground, upper normal contacts of key 52,

the tips of plug 51 and jack 510, conductor 21, upper right hand winding of repeating coil 15, Winding of relay 30, condenser 31, back contact and armature of relay 12, conductor 22, rings of jack 50 and'plug 51, lower alternate contacts of key 52 and source of ringing current 53 to ground. Relay 30 in energizing completes a circuit at its front contact and armature tor relay 14:. 'VR-elay 14 in operating disconnects' the primary winding of the repeating coil 15 and the impulse repeating means associated therewith from the trunk circuit and conducti ely connects the outer to the inner section of the trunk. A path for ringlng current parallel to that previously traced is then completed over a circuit extendingv over the following path conductor 21, resistance 35, upper alternate contacts of relay 14, upper normal contacts of jack 11, righthand winding of relay 37, condenser 38, lower alternate contacts of relay 14, resistance 36to conductor 22. Belay 37 is thereby energized and locks oyer a path extending "from ground,

armature and front contact of relay 3?, lower normal contacts of jack 11 and thence in parallel, one path extending throughlamp 39 to grounded battery and the other through the left hand winding of relay 3'? t0 grounded battery. Lamp '39 glows and serves to indicate to the operator that a call has arrived. The operator noting this signal inserts plug 10 into jack 11 thereby opening the locking circuit for relayi37 and causing the extinguishment of the lamp 39. The ringing current above described wasmanually applied and therefore as soon as the operator restored key v52 .to normal, rclays 30 and 14 weredeenergized. it the ringing current, projected over the trunk conductors 21 and 22, had been from an automatic ringingsource, relays 30 and 14: would hay e'remained energized or'would have been intermittently energized until plug 10 was inserted; into jack 11, whereupon said ringing current would have been tripped, due to the coil 18 being bridged across the tip and ring conductors 21 and 22 of the trunk circuit T, and relays 30 and let would thereupon have become deener gized. As soon as relays 30and -14: retract theirarmatures, relays 13, 12 and 16 of the trunk circuit operate over circuits previ may again actuate ringing key 52 to project ringing current over the trunk conductors 21 and 22,'whereupon-relay 30 will be energized over a path extending from ground, upper alternate contacts of ringingkey 52, tips of plug51 andjack 50, conductor 21, through the upper right-hand winding of repeating coil 15 and thence in parallel, one path extending through condenser 29 and the other through the w'nding relay 30, condenser 28 right-hand alternate contacts of slowtooperate relay 16, and then through the lower r ght-hand winding of repeating co 1l15, trontcontact and armature of relay 12, conductor 22, rlngs of ack 50 and plug 51, lower alternate contacts of ring-mg key 52 and source of ringing current 53 to ground. Relay 30 is "thus energized and completes through its armature and front contact a circuit fonrelay 14:. As soon as relay 14 is energized, the primary winding of the repeating coil 15 and the impulse relay 12 are disconnected. from the trunk (sir-- cuit, and ringing current now passes over a path extending from conductor 21, through resistance upper alternate contacts of relay 1%, tips of jack 1 and plug 10, condenser 11, winding of relay 12, rings of plug and jack 11,.lower alternate contacts of relay 141-, resistance to conductor 22, in parallel with the path previously traced for the energization of relay 30. Relay 12 of the cord circuit thereupon attracts its armature and completes a circuit for lampsignal 13 of the cord circuit, which serves as a reca -ll signal to the operator: The operator at position A, noting the recallsignal, may again actuate her listen ng key to converse with the toll operator. Upon completion of conversation plugs 10 and 51 will be removed from their respective jacks whereupon all relays of the trunk circuit willbe restored to normal and the trunk circuit is ready for the next call.

Referring to Fig. 2 of the drawings, it will be assumed that the subscriber at substation M desires to converse with a subscriber D of the automatic exchange. Upon the removal of the receiver 101 from they switchhook 102 of the calling station M, relays 110 and 111 of the trunk circuit T will be energized over a path extending from grounded battery, through the left hand winding of relay 111, normal contacts of slow-to-operate relay 112, lower normal contacts of relay 127, through the substation loop, upper normal contacts of relay 12?, upper left hand winding of repeating coil 113, winding of relay 110 and right hand winding of relay 111 to ground. Relay 110 attracts its armature and completes a circuit for slow-to-operate relay 112 which relay in operating connects condenser 114: in serial relationship with the primary windings of the repeating coil 113, and removes the short circuit from the left hand winding of repeating coil 113. Relay 111'- in ener gizing bridges the; conductors 106 and 107 of the outer section of the trunk T thereby causing the operation of the non-numerical switch N in the well known manner and as soon as an idle switch such as K has been selected relay 115 thereof will be operated over a circuit extending from ground, left hand winding of relay 115, terminal 115, brush 1441, conductor 106 upper and lower right hand windings of repeating coil 113, front contact and armature of relay 111, conductor 107 brush 1 16, terminal 1417, and right hand winding of relay 115 to grounded battery. vF or the purpose of simplicity a connector switch K only has been diagrammatically represented. It will be understood of course that a non-numerical switch and one or more selectors may be interposed between the non-numerical switch N and the connector switch K. I

The subscriber at station M may now operate sender S in order to set the switch K upon the terminals of the desired line D. Upon the first interruption of each series of impulses of the line circuit,-relays 110 and 111 de-energize. Relay 110 in deenergizing causes the release of slow-to-operate relay 112 which in retracting its armature removes condenser 114 from serial relationship with the left hand windings of repeat ing coil and again completes a short circuit around the lower left hand winding of repeating coil 113. Relay 111 upon deenergizing interrupts the bridge across the outer section causing impulse relay 115 to deencrgize. Upon each succeeding impulse of each series of impulses relay 111 is actuated to control the impulse relay 1155 Relay 112 being slow-to-operate remains deenergized throughout the sending of each series of impulses. At the end of each series of impulses relay 112 again operates to connect condenser 11 1 in series with theinner section of the trunk and to remove the short circuit from the lower lefthand winding of repeating coil 113. After sufficient impulses have been sent to set brushes 120 and 121 of connector switch K upon the terminals 122 and 123 to-which the station I) is connected said station is signalled in the well known manner. Station'M is then supplied with talking battery through the windings of relay 111, and station D through the windings of relay 116.

Upon the completion of conversation and the restoration of the receiver at station M to the switch hook relays 110 and 111 release, the former relay releasing relay 112 and the latter interrupting the bridge across the conductors 106 and 107 of the trunk T The switches at the automatic exchange are thereupon restored to normal in the well known manner.

An incoming call for station M will now be described. It will be assumed that source of ringing current is projected over the conductors 106 and 107 in any well known manner. In the case of an incoming call relay 125. may be energized over a path including ground at a source of ringing current such as 153 at tie cord circuit E over conductor 106, the upper and lower right hand windings of repeating coil 113,.winding of relay 125, condenser 126, conductor 107, and source of ringing current 153. Relay 125 is thereupon energized, and in attracting its armature, completes a circuit for the energization of relay 127. As soon as relay 127 operates ringing current flows over conductor 106 through the upper alternate contacts of relay 127, conductor 10 1, sender S condenser 108, ringer 103, conductor 105, the lower alternate contacts of relay 127 .to conductor 107 in parallel with the path of the ringing current previously traced. If the ringing current is manually applied and is of comparatively short duration, relays 125 and 12'? release their armatures as soon as the operator ceases to project current over the conductors 106 and, 107. If, however, the ringing current is automatically applied, relays 126 and 12'? remain energized'until the subscriber at station M responds whereupon the subscribers set is-bridged across conductors 106 and 107 causing tripping of the ringing in the well known manner. lVhen the ringing current is tripped, relays 126 and 12? release their armatures thereby completing a circuit for relays 110 and 111 over a path previously traced. Relay 110 in energizing causes the operation of relay 112 which connects condenser 114 in series with the primary windings of the repeating coil 113 and 111 in operating closes the bridge acros'sthe conductors 106 and 107.

When conversation has ceased and the receiver is restored to the switchhoolrrelays 110, 111 and 112 release their armaturcs and the circuit is ready for the next call.

What is claimed is: 1. In a telephone system, a two-way trunk circuit having two sections, impulse repeating means connected to one section of the trunk for use in building up a connection in one direction "over said trunk, and means connected to the other section of the trunk and responsive to ringing current to cause disconnection of the impulse repeating means from the trunk circuit while ringing in the other direction over said trunk.

circuit having two sections, a repeating coil for inductively uniting said sections, impulse repeating means connected to one section for use in building up a connection in one direction over said trunk circuit, and

means connectedtothe other section and ing means connected to the inner section,

and a relay in circuit with the outer section of the trunk and responsive to ringing current thereover for causing the disconnection of the impulse repeating means, from, and

conductively connecting the outer section to,

the inner section of the tru'nli.

4. In a telephone system, a trunk circuit having inner and outer sections, a repeating coil for inductively uniting said sections, impulse repeating means normally connected to the inner section, a relay in circuit with the outer section of the trunk and responsive to ringing. current thereover,

and a second relay operating in response to the energization the first relay to connect the outer section tothe inner section, independently of the impulse repeating means.

In a. telephone system, a trunk circuit having two sections, a repeating coil for inductively uniting said sections, an impulse repeating relay connected to the inner section having a contact included in circuit with the outer section responsive'to impulses, to bridge the outer section, a ringing current relay'conn'ected to the outer section, said relay being adapted upon actuation to disconnect the primary winding of the repeating coil from the trunk circuit and to conductive'ly connect the outer'and inner sec tions tothe exclusion of the impulse repeat.-

ing relay connected to the inner section.'

6.- In a telephone system, a trunlrcircuit having inner and outer sections, a repeating coil for inductively. uniting such sections for the transmission of voice currents, a relay normally connected to the inner section for repeating impulses to theouter section, a cord circuit for extending connection over said trunk, a signaling device in said circuit, and means responsive to the application of ringing current to the outer section of the trunk when the cord circuitis. connected'to the inner section for disconnecting sald impulse repeating means and for conductively ringlng over the lnner section of said trunk to cause the actuation of said signaling device. r 2. In a telephone system, a two-way trunk calling station to a called station, an inner and outer sectlon for said llnk circuit, an

inductive path normally uniting said inner v and outer sections, .an impulse repeating relay. connected to the'inner-section, means for applying ringing current to the outer section, and means responsive to the application of the ringing irrent for replacing the v inductive path by a conductive path and for disconnecting the impulse repeating relay.

8. In a'telephone exchange system,fa main exchange, a private branch exchange, a

trunk circuit extending between said exchanges, said trunk circuit being normally conductively divided into inner and outer sections, means for repeating impulses and signalling means normally connected to the inner section of said trunk circuit, a cord circuit having signaling means at the private branch exchange for extending connections over said trunk circuit, a source of ringing current, and means responsive to the application of said ringing current to the outer sectlonof said trunk circuit for conductlvely .uniting the outer and inner sections of said trunk circult,independently of sald lmpulse repeating means, to cause the actuation of the trunk circuit signaling means on calls and to cause the actuation of the cord circult short-circuiting a portion of said repeat ing coil and for disconnecting said condenser during the transmission of impulses.

10. In a telephone system, a trunk line divided into inner and outer sections by means ofa repeating coil, a relay for repeating inipulses from the inner to the outer section, said relay being responsive to impulses received over the inner section oi said trunk line, an alternating current bridge connected across each section of said trunk, an impedance bridge, connected across the outer sectionof said trunk When a talking connectionis established over said trunk line, and means for rendering said bridges inefiective during the transmission of impulses over said trunk line. Y

11. In a, telephone system, a trunk line divided into inner and outer sections by means of a repeating coil, a relay for repeating impulses from the inner to the outer section, said relay being responsive to impulses received over the inner section of said trunk line, an impedance bridge and a condenser connected across the inner and across the outer sections of said trunk when a connection is establishedthereover, and means for rendering said impedance bridges and said condensers ineffective during the transmission of impulses over said trunk line.

12. In a telephone system, a two-Way circuit having two sections, voice current repeating means inductively coupling said sections, a dial, impulse repeating means connected to one section of said circuit responsive to said dial for use in extending a connection in one direction over said circuit, a source of ringing current, and means con- 'nected to the other section of said circuit responsive to current from said source when a connection is extended in the other direction over said trunk to cause disconnection of the voice current repeating means and the impulse repeating means from the circuit during ringin In Witness whereof We hereunto subscribe our names this 2nd day of August, A. D. 1920.

WALTER n; STRIOKLER. PAUL L. WRIGHT. 

